Saturated Multi-Delay Renal Arterial Spin Labeling Technique at 5 T MR: A Comparative Study With 3 T

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Renal Physiology
• Medical Imaging Technology

Background:

• The feasibility of multi-delay arterial spin labeling (ASL) for renal imaging at 5 Tesla (5T) is not well-established.
• Arterial spin labeling (ASL) is a non-invasive MRI technique used to measure blood flow.

Purpose of the Study:

• To evaluate the feasibility of the saturated multi-delay renal ASL (SAMURAI) sequence at 5T.
• To compare image quality and perfusion quantification of the SAMURAI sequence at 5T versus 3T.

Main Methods:

• A prospective, cross-sectional study involving 20 healthy volunteers for primary comparison and 6 for reproducibility at 5T.
• The SAMURAI sequence was optimized at 5T using renal-specific B1 shimming and an optimized saturation scheme.
• Participants underwent both 3T and 5T scans; cortical T1 values, renal blood flow (RBF), and bolus arrival times were measured. Signal-to-noise ratio (SNR) and cortico-medullary contrast-to-noise ratio (CNR) were calculated.

Main Results:

• Renal cortical T1 values were significantly higher at 5T (1417.9 ms) compared to 3T (1184.2 ms).
• Cortical RBF showed no significant difference between 5T and 3T (p=0.333), with strong correlation (R²=0.914).
• 5T demonstrated significantly higher mean SNR (4.6 vs. 3.9) and CNR (3.2 vs. 2.0) than 3T, with excellent repeatability and reproducibility (ICC=0.855-0.973).

Conclusions:

• The SAMURAI sequence is feasible and repeatable for quantitative renal imaging at 5T.
• 5T imaging offers superior SNR and CNR compared to 3T.
• Strong agreement in cortical RBF measurements between 3T and 5T supports the utility of 5T for renal perfusion assessment.